Patterned receiver for color filter array

ABSTRACT

A thermally-transferred color filter array element, preferably for use in a color electro-optical display device such as a color liquid crystal display device, comprising a support having thereon a polymeric dye image-receiving layer containing a thermally-transferred image comprising a repeating pattern of colorants, such as a mosaic pattern, the polymeric dye image-receiving layer having been applied to the support using screen printing.

This invention relates to a thermally-transferred color filter arrayelement wherein screen printing is used to coat a support with apolymeric dye image-receiving layer which contains the color filterarray. The color filter array element may be used in electro-opticaldevices such as a color liquid crystal display device.

In recent years, thermal transfer systems have been developed to obtainprints from pictures which have been generated electronically from acolor video camera. According to one way of obtaining such prints, anelectronic picture is first subjected to color separation by colorfilters. The respective color-separated images are then converted intoelectrical signals. These signals are then operated on to produce cyan,magenta and yellow electrical signals. These signals are thentransmitted to a thermal printer. To obtain the print, a cyan, magentaor yellow dye-donor element is placed face-to-face with a dye-receivingelement. The two are then inserted between a thermal printing head and aplaten roller. A line-type thermal printing head is used to apply heatfrom the back of the dye-donor sheet. The thermal printing head has manyheating elements and is heated up sequentially in response to the cyan,magenta and yellow signals. The process is then repeated for the othertwo colors. A color hard copy is thus obtained which corresponds to theoriginal picture viewed on a screen. Further details of this process andan apparatus for carrying it out are contained in U.S. Pat. No.4,621,271 by Brownstein entitled "Apparatus and Method For Controlling AThermal Printer Apparatus," issued Nov. 4, 1986, the disclosure of whichis hereby incorporated by reference.

Liquid crystal display devices are known for digital display inelectronic calculators, clocks, household appliances, audio equipment,etc. Liquid crystal displays are being developed to replace cathode raytube technology for display terminals. Liquid crystal displays occupy asmaller volume than cathode ray tube devices with the same screen area.In addition, liquid crystal display devices usually have lower powerrequirements than corresponding cathode ray tube devices.

There has been a need to incorporate a color display capability intosuch monochrome display devices, particularly in such applications asperipheral terminals using various kinds of equipment involvingphototube display, mounted electronic display, or TV-image display.Various attempts have been made to incorporate a color display using acolor filter array element into these devices. However, none of thecolor array elements for liquid crystal display devices so far proposedhave been successful in meeting all the users' needs.

One commercially-available type of color filter array element which hasbeen used in liquid crystal display devices for color display capabilityis a transparent support having a gelatin layer thereon which containsdyes having the additive primary colors red, green and blue in a mosaicpattern obtained by using a photolithographic technique. To prepare sucha color filter array element, a gelatin layer is sensitized, exposed toa mask for one of the colors of the mosaic pattern, developed to hardenthe gelatin in the exposed areas, and washed to remove the unexposed(uncrosslinked) gelatin, thus producing a pattern of gelatin which isthen dyed with dye of the desired color. The element is then recoatedand the above steps are repeated to obtain the other two colors.Misalignment or improper deposition of color materials may occur duringany of these operations. This method therefore contains manylabor-intensive steps, requires careful alignment, is time-consuming andvery costly. Further details of this process are disclosed in U.S. Pat.No. 4,081,277. U.S. Pat. No. 4,786,148 also discloses a color filterarray element which employs certain pigments.

Color liquid crystal display devices generally include two spaced glasspanels which define a sealed cavity which is filled with a liquidcrystal material. For actively-driven devices, a transparent electrodeis formed on one of the glass panels, which electrode may be patternedor not, while individually addressable electrodes are formed on theother of the glass panels. Each of the individual electrodes has asurface area corresponding to the area of one picture element or pixel.If the device is to have color capability, a color filter array with,e.g., red, green and blue color areas must be aligned with each pixel.Depending upon the image to be displayed, one or more of the pixelelectrodes is energized during display operation to allow full light, nolight or partial light to be transmitted through the color filter areasassociated with that pixel. The image perceived by a user is a blendingof colors formed by the transmission of light through adjacent colorfilter areas.

In forming such a liquid crystal display device, the color filter arrayelement to be used therein may have to undergo rather severe heating andtreatment steps during manufacture. For example, a transparentconducting layer, such as indium tin oxide (ITO), is usually vacuumsputtered onto the color filter array element which is then cured andpatterned by etching. The curing may take place at temperatures elevatedas high as 200° C. for times which may be as long as one hour or more.This is followed by coating with a thin polymeric alignment layer forthe liquid crystals, such as a polyimide, followed by another curingstep for up to several hours at an elevated temperature. These treatmentsteps can be very harmful to many color filter array elements,especially those with a gelatin matrix.

In U.S. Pat. No. 4,962,081 polycarbonate dye image-receiving layermaterials for color filter array elements are described. In using thesematerials to form a color filter array element, the polymeric materialwould typically be coated onto a glass support over the entire surfaceusing spin coating in order to obtain a smooth coating. A thin overcoatlayer would then usually be applied thereover to help protect thepolymeric receiving layer from the harsh treatment steps which follow.

However, it has been found necessary to not have the coating of thepolymeric dye image-receiving layer extend over the entire surface ofthe glass support used to form the color filter array. Instead, it hasbeen found desirable to coat the polymeric dye image-receiving materialin a pattern onto the glass support, just slightly larger than theviewing area of the liquid crystal display device. There are at leasttwo reasons for doing this.

First of all, patterning the receiving layer improves the seal formationbetween the two plates since there is a glass-to-glass seal, rather thanhaving the polymer in between. The adhesive used to seal the platestogether doesn't adhere very well to polymeric materials, which in turncauses the cell to leak.

Secondly, patterning the receiving layer makes it much easier to repairthe display device if it becomes necessary. For example, severalelectronic chips or other electronic hardware are typically located onthis plate having the color filter array thereon. The chips areconnected via the transparent ITO layer, which has been etched to form apattern of leads outside the viewing area.

There is not a 100% reliability of placing a given chip on the plate inthe proper area. By increasing the number of chips to be so located onthe plate, the probability of having at least one chip improperlypositioned increases substantially. Rather than discard the wholedisplay device, it is more economic to remove and reposition or replacethe chip.

Removing a chip from the fragile ITO layer is easier if the ITO layer iscoated directly onto the glass substrate to which it has betteradhesion, rather than being coated onto a polymer. When the ITO layer iscoated directly onto a polymer, it has poorer adhesion and breaks morereadily during the repair process which involves removing an adhesiveused to bond the chip to the support in order to remove the chip.

The method for applying the polymeric dye image-receiving material in apattern onto a support such as glass should result in a smooth coatingwith edges that have a continuous and smoothly decreasing slope. Theslope of the edge is preferably less than 10°. If the edges are undercutor sharp, then the overcoat layer which is applied thereover, usually bya printing technique, becomes discontinuous at that edge eventuallycausing a break in the ITO layer. For example, if the receiving layerhas a sharp edge so that it is not protected by the overcoat layer, thenthe receiving layer can be attacked by subsequent treatment stepsinvolving the ITO and alignment layers. This in turn leads to the ITOlayer becoming improperly etched due to lateral etching caused byimproper covering of the sharp edge by the overcoat layer, resulting ina break. When there is a break in the ITO layer, the entire displaydevice must be discarded.

There are many techniques for printing a polymer in a pattern on asupport such as flexographic printing, gravure printing, ink jetprinting, hopper printing, air brush, spin coating followed by etching,etc. All of these techniques suffer from one or more of the problemsdiscussed above.

Photolithographic etching is a process which is well known and widelyused in the art to remove polymeric materials from certain areas of acoating. However, as will be shown hereinafter, use of this process inpatterning the receiving layer causes a subsequently applied ITO layerto become discontinuous, so that it would not be useful in a displaydevice.

Flexographic printing is also a common technique used in the art topattern various layers. However, the layers which are applied in thismanner are too thin to provide a sufficient thickness for a dyeimage-receiving layer used for thermal printing. While multiple passesthrough the printing press could be used to obtain the proper thickness,this would substantially add to the cost and the multiple deposition oflayers has a deleterious effect on the properties of the layer as awhole.

It would be desirable to provide a method of coating a polymeric dyeimage-receiving material in a pattern onto a support to form a colorfilter array element which would avoid the disadvantages discussedabove. It would also be desirable to provide a thermally-transferredcolor filter array element employing that method. It would further bedesirable to provide an electro-optical display device employing such acolor filter array element.

These and other objects are achieved in accordance with this inventionwhich comprises a thermally-transferred color filter array elementcomprising a support having thereon a polymeric dye image-receivinglayer containing a thermally-transferred image comprising a repeatingpattern of colorants, the polymeric dye image-receiving layer havingbeen applied to the support using screen printing.

FIG. 1 illustrates a display device in accordance with the invention.

The use of screen printing was found to avoid the problems discussedabove, especially the problem of how to provide a coating pattern with agradual decreasing slope at the edge in order to avoid an electricalfailure in the ITO layer which is applied thereover.

Commercially available screen printing machines can be used in theinvention such as the Microtronic® V machine made by the Ekra Company.The mesh count for the screen can be from about 100 to about 500 per cm.The open area for the screen can be from about 20% to about 50%. Thethread diameter for the screen can be from about 30 to about 70 μm.Commercially available screens which can be used include polyesterscreens from NBC Industries Co. and Advance Process Supply Co. Thesqueegee for the screen can be rounded, rectangular or square in shapewhich is used in a dragging motion on the screen.

There are many material and equipment factors which affect the qualityof a screen-printed pattern. The coating solution must have a viscositysuch that it can penetrate the screen and then flow out to a smooth filmon the substrate after printing. Optimization of the viscosity isdirectly linked to the mesh or fineness of the screen. Additionalmechanical factors can play a role such as the angle, rate and pressureof the squeegee and the distance of the screen from the substrate,called the "snap-off distance".

As noted above, the dye image-receiving layer contains athermally-transferred image comprising a repeating pattern of colorantsin the polymeric dye image-receiving layer, preferably a mosaic pattern.

In a preferred embodiment of the invention, the mosaic pattern consistsof a set of red, green and blue additive primaries.

In another preferred embodiment of the invention, each area of primarycolor and each set of primary colors are separated from each other by anopaque area, e.g., black grid lines. This has been found to giveimproved color reproduction and reduce flare in the displayed image.

The size of the mosaic set is not critical since it depends on theviewing distance. In general, the individual pixels of the set are fromabout 50 to about 600 μm and do not have to be of the same size.

In a preferred embodiment of the invention, the repeating mosaic patternof dye to form the color filter array element consists of uniform,square, linear repeating areas, with one color diagonal displacement asfollows: ##STR1##

In another preferred embodiment, the above squares are approximately 100μm.

The color filter array elements prepared according to the invention canbe used in image sensors or in various electro-optical devices such aselectroscopic light valves or liquid crystal display devices. Suchliquid crystal display devices are described, for example, in UK Patents2,154,355; 2,130,781; 2,162,674 and 2,161,971.

Liquid crystal display devices are commonly made by placing a material,which is liquid crystalline at the operating temperature of the device,between two transparent electrodes, usually indium tin oxide coated on asubstrate such as glass, and exciting the device by applying a voltageacross the electrodes. Alignment layers are provided over thetransparent electrode layers on both substrates and are treated toorient the liquid crystal molecules in order to introduce a twist of,e.g., 90°, between the substrates. Thus, the plane of polarization ofplane polarized light will be rotated in a 90° angle as it passesthrough the twisted liquid crystal composition from one surface of thecell to the other surface. Application of an electric field between theselected electrodes of the cell causes the twist of the liquid crystalcomposition to be temporarily removed in the portion of the cell betweenthe selected electrodes. By use of optical polarizers on each side ofthe cell, polarized light can be passed through the cell orextinguished, depending on whether or not an electric field is applied.

The polymeric alignment layer described above may be any of thematerials commonly used in the liquid crystal art. Such materialsinclude polyimides, polyvinyl alcohol, methyl cellulose, etc.

The transparent conducting layer described above is also conventional inthe liquid crystal art. Such materials include indium tin oxide, indiumoxide, tin oxide, cadmium stannate, etc.

FIG. 1 shows diagrammatically a part of liquid crystal display device 1having a plate 2 of glass, quartz or other suitable material. A colorfilter array 3 comprises red(R), green(G) and blue(B) cells 4corresponding to pixels as prepared according to the method of theinvention. Black grid lines 5 separate each color cell. The color filterarray 3 is provided with an overcoat layer 6 and a transparentconducting layer of ITO 7.

The other plate 8 has electrodes 9 provided thereon which define pixels,either because the electrodes 9 and the transparent conducting layer ofITO 7 constitute a cross-bar system in which the crossings define thepixels (passive drive), or because the electrodes 9 constitute pictureelectrodes which are driven by a system (not shown) of switchingelements, drive and data lines (active drive), in which case theelectrodes 9 may have a single flat structure.

A layer of liquid crystal material 11 is present between the twosupporting plates 2 and 8 which is provided with alignment layers 10.The two plates are held at a substantially constant distance from eachother by means of a sealing edge 12 and spacers 13. In practice, thedevice is further provided with polarizers, reflectors, etc. in theconventional manner.

The dye image-receiving layer used in forming the color filter arrayelement of the invention may comprise, for example, those polymersdescribed in U.S. Pat. Nos. 4,695,286, 4,740,797, 4,775,657, and4,962,081, the disclosures of which are hereby incorporated byreference. In a preferred embodiment, polycarbonates having a glasstransition temperature greater than about 200° C. are employed. Inanother preferred embodiment, polycarbonates derived from a methylenesubstituted bisphenol-A are employed such as4,4'-(hexahydro-4,7-methanoindan-5-ylidene)-bisphenol. In general, goodresults have been obtained at a coverage of from about 0.25 to about5mg/m².

The support used in the invention is preferably glass such as boraxglass, borosilicate glass, chromium glass, crown glass, flint glass,lime glass, potash glass, silica-flint glass, soda glass, and zinc-crownglass. In a preferred embodiment, borosilicate glass is employed.

A dye-donor element that is used to form the color filter array elementof the invention comprises a support having thereon a dye layer. Any dyeor mixture of dyes can be used in such a layer provided they aretransferable to the dye image-receiving layer of the color array elementof the invention by the action of heat. Especially good results havebeen obtained with sublimable dyes. Examples of sublimable dyes includeanthraquinone dyes, e.g., Sumikalon Violet RS® (Sumitomo Chemical Co.,Ltd.), Dianix Fast Violet 3R-FS® (Mitsubishi Chemical Industries, Ltd.),and Kayalon Polyol Brilliant Blue N-BGM® and KST Black 146® (NipponKayaku Co., Ltd.); azo dyes such as Kayalon Polyol Brilliant Blue BM®,Kayalon Polyol Dark Blue 2BM®, and KST Black KR® (Nippon Kayaku Co.,Ltd.), Sumickaron Diazo Black 5G®(Sumitomo Chemical Co., Ltd.), andMiktazol Black 5GH® (Mitsui Toatsu Chemicals, Inc.); direct dyes such asDirect Dark Green B® (Mitsubishi Chemical Industries, Ltd.) and DirectBrown M® and Direct Fast Black D® (Nippon Kayaku Co. Ltd.); acid dyessuch as Kayanol Milling Cyanine 5R® (Nippon Kayaku Co. Ltd.); basic dyessuch as Sumicacryl Blue 6G® (Sumitomo Chemical Co., Ltd.), and AizenMalachite Green® (Hodogaya Chemical Co., Ltd.); ##STR2## or any of thedyes disclosed in U.S. Pat. Nos. 4,541,830, 4,541,830, 4,698,651,4,695,287; 4,701,439, 4,757,046, 4,743,582, 4,769,360 and 4,753,922, thedisclosures of which are hereby incorporated by reference. The abovesubtractive dyes may be employed in various combinations to obtain thedesired red, blue and green additive primary colors. The dyes may bemixed within the dye layer or transferred sequentially if coated inseparate dye layers. The dyes may be used at a coverage of from about0.05 to about 1 g/m².

Various methods may be used to transfer dye from the dye donor to thetransparent support to form the color filter array element of theinvention. There may be used, for example, a high intensity light flashtechnique with a dye-donor containing an energy absorptive material suchas carbon black or a light-absorbing dye. Such a donor may be used inconjunction with a mirror which has a grid pattern formed by etchingwith a photoresist material. This method is described more fully in U.S.Pat. No. 4,923,860.

Another method of transferring dye from the dye donor to the transparentsupport to form the color filter array element of the invention is touse a heated embossed roller as described more fully in U.S. Pat. No.4,978,652.

In another embodiment of the invention, the imagewise-heating is done bymeans of a laser using a dye-donor element comprising a support havingthereon a dye layer and an absorbing material for the laser, theimagewise-heating being done in such a way as to produce a repeatingmosaic pattern of colorants.

Any material that absorbs the laser energy or high intensity light flashdescribed above may be used as the absorbing material such as carbonblack or non-volatile infrared-absorbing dyes or pigments which are wellknown to those skilled in the art. In a preferred embodiment, cyanineinfrared absorbing dyes are employed as described in U.S. Pat. No.4,973,572.

After the dyes are transferred to the receiver, the image may be treatedto further diffuse the dye into the dye-receiving layer in order tostabilize the image. This may be done by radiant heating, solvent vapor,or by contact with heated rollers. The fusing step aids in preventingfading and surface abrasion of the image upon exposure to light and alsotends to prevent crystallization of the dyes. Solvent vapor fusing mayalso be used instead of thermal fusing.

The following examples are provided to illustrate the invention.

Example 1

Two polycarbonates as described below were coated onto borosilicateglass using screen printing by hand. Three different screens wereemployed as follows:

1) A Polystar® monofilament polyester screen (Advance Process SupplyCo.) with a 140 mesh, opening of 115 μm, 42% open area and threaddiameter of 63 μm.

2) A Polystar® monofilament polyester screen (Advance Process SupplyCo.) with a 280 mesh, opening of 53 μm, 34% open area and threaddiameter of 38 μm.

3) A Polystar® monofilament polyester screen (Advance Process SupplyCo.) with a 390 mesh, opening of 32 μm, 25% open area and threaddiameter of 33 μm.

The distance between the screen and the substrate, known as the"snap-off distance" was 4 mm. The squeegee which was employed was arounded, medium hardness, 70-75 durometer, of rubber (Advance ProcessSupply Co.).

The polymers which were coated were as follows: ##STR3##

The Polycarbonate 1 was dissolved in ethyl benzoate as a 15% solution.It had a viscosity of 12,000 cps as measured by a Brookfield LVFViscometer. The Polycarbonate 2 was dissolved in ethyl benzoate as a 20%solution. It had a viscosity of 700 cps as measured by a Brookfield LVFViscometer. Each polymer was then screen printed as a 7.6 cm×7.6 cmsquare.

The coatings were then examined visually for smoothness of the layer onthe glass and for the slope at the edge. Ideally, no screen patternshould be evident. The following results were obtained:

    ______________________________________                                        Coating Smoothness  Slope (degrees)                                           Mesh   Polycarb. 1                                                                             Polycarb. 2                                                                              Polycarb. 1                                                                           Polycarb. 2                               ______________________________________                                        140    Good      Good       2       4                                         280    Good      Excellent  1       1                                         390    Excellent Excellent  1       1                                         ______________________________________                                    

The above coatings were then used as dye image-receiving layers forthermal transfer as would be used in making a color filter array.

A dye-donor was prepared consisting of the following layers coated on a6 μm poly(ethylene terephthalate) support:

1) Dye layer containing the magenta dyes illustrated above (0.27 g/m²),DC-510 Silicone Fluid surfactant (Dow Corning Co.) (0.0003 g/m²), and0.15 g/m² of the cyanine infrared absorbing dye illustrated below, in acellulose acetate-propionate (2.5% acetyl, 48% propionyl) binder (0.41g/m²) coated from a butanone, cyclopentanone and dimethyl formamidesolvent mixture; and

2) Aqueous overcoat layer of 0.5 g/m² of 9 μm polystyrene beads, 0.047g/m² of Woodlok 40-0212®, (National Starch Co.), a water-based emulsionpolymer of vinyl acetate, and 0.01 g/m² of surfactant 10G® (OlinMatheson Corp.), a nonylphenolglycidol glycidol surfactant. ##STR4##

The dye-donor sheet was then placed face-to-face with the receivingelement. The assembly was weighted at approximately 6000 g/m².

A flash unit from EG&G Electro-Optics containing a xenon flash tube,2200 microfarads, 900 v capacitors, charged to 800 v, was then flashedat 9.5 joules/cm² to transfer a 1.2 cm×4.2 cm area of magenta dye to thedye image-receiving layer on the glass plate. The transferred image wasthen fused by exposing to dichloromethane vapors for about 5 minutes.

The glass plate was then coated with a transparent indium tin oxide(ITO) conducting layer (0.2 μm thick) using reactive sputtering of ametal target as described in Example 1 U.S. Pat. No. 4,965,242.

A visual inspection by a scanning electron microscope showed no breaksin the ITO layer at the edge of the underlying polycarbonate layer.

Example 2

Polycarbonate 1 above was dissolved in ethyl benzoate as a 20% solution.It was then screen printed onto a borosilicate glass having a chromiumblack grid using a Microtronic V® screen printing machine (Ekra Co.) toprint a pattern of four rectangles approximately 9 cm×12 cm on a glassplate having a total printed area of 35 cm×32 cm. The snap-off distance(distance between the screen and the substrate) was 1.75 mm. Thesqueegee pressure was 2.5 Bar. The print speed was 30 mm/second. Arectangular squeegee was used. The screen was a polyester from NBCIndustries Co., with a mesh count of 120 per cm.

After the screen printing, the coating was dried for 30 minutes at 90°C. The dry thickness was 2.1 μm. The coating was examined and seen tohave spread at the edges less than 200 μm (or 400 μm in each of twodirections). The slope of the edge was less than 2°. The edge of thepolycarbonate coating had a lip of less than 0.6 μm.

An image was thermally transferred to the polycarbonate receiver usingthe materials of Example 1. An overcoat of an acrylate material was thenapplied to the receiver using flexographic printing according to theprocess described in NL Application 90.00389 filed Feb. 2, 1990, thedisclosure of which is hereby incorporated by reference. An ITO layerwas then applied and patterned in the conventional manner by coating aresist, exposing through a mask in a pre-determined pattern, developingand etching. The resist was then removed leaving the patterned ITO. Analignment layer of a polyimide was then applied and cured. The alignmentlayer was then rubbed in the conventional manner, spacers and sealsapplied, and the cell filled with liquid crystal material of ZLI-3771 ofMerck.

The cell was tested for ITO discontinuities by visual inspection andelectrical testing of resistance measurements and showed nodiscontinuities.

Example 3--Comparative Example-Spin Coating of Receiving Layer

A comparative test was run using the borosilicate glass of Example 2having the chromium grid lines thereon. Polycarbonate 1 above was spincoated onto the support using a 12% solution in xylene. The spin speedwas 30 sec. at 850 rpm and 30 sec. at 300 rpm. It was then dried forone-half hour at 140° C. An aluminum layer was electrolithographicallypatterned on top of the polycarbonate to provide an auxiliary mask toprevent etching of the polycarbonate in the display area. Beforeapplying the protective overcoat, the remaining aluminum was removed bywet chemical etching. A protective overcoat and ITO layer were thenapplied as in Example 2. A visual inspection at this point showed ITObreaks caused by severe underetching of the ITO at the edge of theunderlying polycarbonate layer.

The results of this example showed that spin coating of the receivinglayer followed by etching does not produce useful results.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What is claimed is:
 1. A thermally-transferred color filter arrayelement comprising a support having thereon a polymeric dyeimage-receiving layer containing a thermally-transferred imagecomprising a repeating pattern of colorants, said polymeric dyeimage-receiving layer having been applied to said support using screenprinting, which results in a smooth coating with edges that have acontinuous and smoothly decreasing slope.
 2. The color filter arrayelement of claim 1 which is adapted for use in a color electro-opticaldisplay device.
 3. The element of claim 2 wherein a protective overcoat,transparent conducting layer and a polymeric alignment layer are coatedin the order recited over said polymeric dye image-receiving layer. 4.The element of claim 3 wherein said transparent conducting layer isindium tin oxide.
 5. The element of claim 1 wherein said polymeric dyeimage-receiving layer is a polycarbonate having a glass transitiontemperature greater than about 200° C.
 6. The element of claim 5 whereinsaid polycarbonate is derived from4,4'-(hexahydro-4,7-methanoindene-5-ylidene)bisphenol.
 7. The element ofclaim 1 wherein said pattern is a mosaic pattern of a set of red, greenand blue additive primaries.
 8. The element of claim 7 wherein saidprimary colors are separated from each other by an opaque area.
 9. Theelement of claim 8 wherein said opaque areas form a black grid.
 10. Theelement of claim 1 wherein said thermally-transferred image comprisesone or more sublimable dyes.
 11. The element of claim 1 wherein saidthermally-transferred image is obtained using a high intensity lightflash.
 12. The element of claim 1 wherein said support is glass.
 13. Anelectro-optical display device comprising a display medium between twosupporting substrates wherein one of said substrates comprises thethermally-transferred color filter array element of claim
 1. 14. Theelectro-optical display device of claim 13 in which the display mediumis a liquid crystal.
 15. A process of forming a color filter arrayelement comprising:a) screen printing a polymeric dye image-receivingmaterial onto a support in a pre-determined pattern to form a dyeimage-receiving element, said screen printing resulting in a smoothcoating with edges that have a continuous and smoothly decreasing slope;b) image-wise heating a dye-donor element comprising a support havingthereon a dye layer; and c) transferring a dye image to said polymericdye image-receiving element; said imagewise-heating being done in such away as to produce a repeating pattern of colorants to form said colorfilter array element.
 16. The process of claim 15 wherein said patternis a mosaic pattern of a set of red, green and blue additive primaries.17. The process of claim 16 wherein said primary colors are separatedfrom each other by an opaque area.
 18. The process of claim 17 whereinsaid opaque areas form a black grid.
 19. The process of claim 15 whereinsaid dye-donor element contains a light-absorbing material.
 20. Theprocess of claim 15 wherein a high intensity light flash is used toperform said imagewise-heating step.
 21. The process of claim 15 whereinsaid support is glass.